/**
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package org.apache.zookeeper.book;

import java.util.ArrayList;
import java.util.List;

/**
 * Auxiliary cache to handle changes to the lists of tasks and of workers.
 */
public class ChildrenCache {

    protected List<String> children;

    ChildrenCache() {
        this.children = null;
    }

    ChildrenCache(List<String> children) {
        this.children = children;
    }

    List<String> getList() {
        return children;
    }

    List<String> addedAndSet(List<String> newChildren) {
        ArrayList<String> diff = null;

        if (children == null) {
            diff = new ArrayList<String>(newChildren);
        } else {
            for (String s : newChildren) {
                if (!children.contains(s)) {
                    if (diff == null) {
                        diff = new ArrayList<String>();
                    }

                    diff.add(s);
                }
            }
        }
        this.children = newChildren;

        return diff;
    }

    List<String> removedAndSet(List<String> newChildren) {
        List<String> diff = null;

        if (children != null) {
            for (String s : children) {
                if (!newChildren.contains(s)) {
                    if (diff == null) {
                        diff = new ArrayList<String>();
                    }

                    diff.add(s);
                }
            }
        }
        this.children = newChildren;

        return diff;
    }
}
